International patent application WO 03/096815, of this applicant, discloses an instillation for cooking-cooling food comprising a plurality of tanks which are used to receive the food to be cooked, and automatic means for loading and unloading said food through a side loading and unloading opening existing in each of said tanks, said opening of each tank being equipped with a hermetically sealing side sliding door. The installation includes means for filling each tank with at least one cooking or cooling liquid, and means for subsequently emptying it. Each tank includes means for heating the cooking liquid therein, for example, by bubbling steam through the cooking liquid, although optionally the cooking liquid can be totally or partially pre-heated.
International patent application PCT/ES 2004/000145, of this applicant, describes a hermetically sealing side sliding door that is able to withstand internal pressure and is suitable to be applied to the tanks of the installation described above.
The food to be cooked and/or cooled is preferably arranged in molds housed in support trays stacked inside each tank, preferably forming at least one lower stack and at least one upper stack supported in corresponding lower and upper supporting means inside the tank. In the mentioned prior document, the cooking or cooling of the food is carried by a traditional system.
In this traditional model, a stack of product molds is deposited in a tempered hot water bath, where the transfer of heat to the product is virtually static; i.e. almost exclusively by heat conduction. Furthermore, most of the elements involved in the system have a high specific heat, as corresponds to water and especially the equivalent of the product, since in addition to its merely physical heat capacity, the heat energy required by the physical and chemical cooking reactions is also considered. There is only a minor heat transfer by the more effective heat convection method (due to the movement of the surrounding water, not of the product) which consists of two types, alternatively: by natural convection, in which slightly cooled water tends to move downwards to the bottom due to its greater density; and by the replacement of hot water intended to temper the water of the cooking bath.
However, the limited proportion of metal in the product mold in contact with the heating or cooling water makes natural convection affect a minimal surface of the total surface corresponding to all of the molds in the basket. Even the existence of narrow water channels between the inner vertical walls of the mold in the basket does not entail a significant additional advantage because they are long, narrow and above all, horizontal, virtually any natural convection being prevented and the stagnant water of such channels acting as a mere heat conducting element.
With respect to the most efficient manner of transferring heat from a hot focus to a cold one, which is transfer by radiation (proportional to the difference between the absolute temperatures to the power of four), it virtually does not exist in this system, in which there are no significant temperature gradients between parts.
Therefore, with the traditional system, the cooking process as well as the cooling process (although the latter in a minor extent because there is no chemical reaction heat involved with the product but only the sensible heat of the product) are very slow.
Although the installation described in the mentioned document prevents other drawbacks associated to the amount and slowness of the necessary manual operations in a conventional process where the product cells are introduced and extracted through the upper part of the water tubs by raising and immersing them, and in triplicate: first in hot water baths, then in water at room temperature and finally in cooled water, the drawbacks associated to the mentioned natural convection movement of the liquid persist, which movement has been shown to be insufficient for ensuring a fast and efficient heat exchange between the liquid and the food in different regions of the tank.
The present invention provides a system and a method for cooking-cooling food by immersion under forced and diffuse convection in turbulent flow that is able to maximize the heat exchange and optimize the heat efficiency of the process, providing an effective reduction of the energy costs and a regular cooking-cooling process.